Owing to their light weight, economy and excellent properties, the containers made from a synthetic resin have been widely used for everyday life for containing beverages and foods. In particular, the containers (PET bottles) made from a polyethylene terephthalate (PET) are very highly demanded as containers for containing soft drinks, fancy drinks and foods on account of their excellent mechanical properties and transparency, and have been importantly used by the consumes.
The synthetic resin containers as represented by the above polyethylene terephthalate are, usually, efficiently produced by a stretch-blow molding method (or often simply called stretch-molding or blow-molding) by inflation-molding a preform (cylindrically formed material with bottom formed in advance) in a metal mold by blowing a fluid such as the air therein.
The preforms have heretofore been molded by an injection-molding method. However, a compression-molding machine has now been proposed at a lower cost than the injection-molding machine, featuring a small size and being capable of conducting the molding at a low temperature. In order to increase mass-productivity and to improve production efficiency, a rotary compression-molding machine (rotary movable compression-molding machine) has been developed and employed having a number of metal molds mounted on a rotary disk.
In the case of the compression molding, the preforms of a synthetic resin are successively molded by a compression-molding machine, the molded preforms are readily and successively fed into a blow-molding machine by a conveyer line, and the preforms are successively molded into containers by the blow-molding machine (patent document 1). Therefore, the preforms molded by the compression-molding machine can be consecutively forwarded to the blow molding in a state of maintaining a high temperature without almost any fluctuation in the temperature of the individual preforms, which is favorable from the standpoint of not only molding the bottles maintaining stability but also maintaining asepsis of the filling system. The patent document 1 discloses a preferred temperature for taking out the preform without causing strain by conducting no external heat treatment such as of a gas burner or the hot air at the time of taking the preforms out of the metal molds of the compression-molding machine.